The present invention is generally related to a power supply control apparatus and a power supply control method for use in portable electronic equipments driven by a battery. More specifically, the present invention is directed to a key input circuit, a power supply control apparatus, and a power supply control method for use in portable electronic equipments, in which a power supply control key is provided with a key switch formed by arranging a plurality of key contacts at cross points of a key matrix, a hardware size is suppressed, and a software processing sequence used to detect a depression of a key is made simple.
In a conventional power supply control apparatus, a key switch for controlling a supply of electric power is realized by a power supply control key which is arranged independently from a key matrix. When the power supply is turned ON, since this power supply control key is depressed, the power supply is directly controlled so as to commence supplying of the electric power. Also, when the power supply is turned OFF, supplying of the electric power is stopped by interrupting a process operation executed by a processing apparatus (CPU etc.), and by detecting a key depression (by monitoring key state) executed by the processing apparatus (CPU etc.) via an I/O port.
However, the power supply control key used to instruct the power supply control of the power supply and also the key matrix for entering the key operation are independently arranged in the above-explained conventional power supply control apparatus. Since the key input directed to the power supply control and the key input directed to the key input operation are detected by the other circuits, there is such a problem. That is, the processing systems would become complex, and thus, the overall hardware size of the power supply control apparatus is increased.
Also, since the key depression detecting procedure for entering the key operation is required independent from the depression detection procedure of the power supply control key, there is another problem that the software processing procedure used to detect the key depression detection would become complex.